Thursday, March 17, 2011

The Ampeg Bass Amplifiers

1965 B-15N

I have heard it said that Ampeg amplifiers were for East Coast players and Fender Amps were for West Coast players.  I think that was due to the union influence on New York studio players.
Back in the day, New York union session players had to hire “cartage” companies to deliver their gear to a studio. To cut down on luggage, some of those recording studios kept amplifiers on hand.   Usually these were Ampegs.

I cannot recall if it was Tommy Tedesco or Vinnie Bell that wrote about a studio that rented out its Ampeg amplifier to players.  The off-on switch was replaced with a key.  It was pay-to-play back then.

Ampeg had its start in 1946 by bass player named Everett Hull and his partner, Stanley Michaels.  Hull had designed a transducer pickup for a bass fiddle that fit inside the instrument by means of the floor peg.  What else would you call this but Amplified peg or Ampeg? 

Everett Hull with
Baby Bass
By 1960, Hull was the sole owner. He added a small version of an upright bass originally made by a company called Zorko to the Ampeg lineup. The instrument was made of fiberglass and named the Baby Bass. The next step would be to design an amplifier for the bass & bass pickup.  

Hull enlisted an electronic designer named Oliver Jessup aka Jess Oliver.  Oliver designed an amp that took its queue from a feature on a sewing machine.  Oliver called this amp the Port-o-flex.  Its enclosed speaker cabinet held either a 12” or 15” speaker.  Oliver designed a special double-baffle porting system for the cabinet to give it a special sound.  The amplifier unit or “head” was stored upside down in the amplifiers top.  The amplifier was attached to a vinyl-covered board that matched the vinyl covering of the amplifier and fit neatly into the cabinet, which was fastened in place.  When it came time the player would lift the amp unit out and turn it right side up.

The first model was the B-15.  This amplifier had a 15” speaker and a whopping 25 watts.  Later models had 30 watts. A smaller version called the SB-12 came with a 12" speaker.

One of the amplifier issues of the day was overheating due to the tubes, especially with enclosed combo amps.  Oliver solved this problem by housing the electronics in a perforated metal housing, that protected the tubes and transformers (and the musician from electrical shock), but it also allowed the tubes to be exposed. 

Inside Cabinet
The B-15 replaced the B-15N in 1961 and then the B-15NB, which had a solid-state rectifier instead of a tube rectifier. Nineteen Sixty-four brought about another change, when the tube rectifier was brought back, but the amp used a printed circuit board, now known as the B-15NC.

In 1965, Ampeg used a single baffle board and changed the tubes to fixed bias.

SB-12 with One Channel
The amps all used twin 6L6 power tubes.  They came with two channels, with volume, treble, and bass controls for each.   The Ampeg Portoflex was the go-to bass amp of its day, but it sounded great with guitar.

Though the power rating seems small, especially for a bass amp by today’s standards, the amp was not designed for rock players.  Musicians in the 1960’s were discouraged from turning the volume up to the point of distortion.  

Clean was the by-word of the day.  The aforementioned Vinnie Bell and Tommy Tedesco used the Portoflex for recording in those days as did Joe Pass.

Within a few years such well-known designers such as Dan Armstrong, and Dennis Kager joined Ampeg.  

But, it was Roger Cox, Bill Hughes and Armstrong that designed the biggest amplifier of the day called the SVT, for super vacuum tubes.  

This beast came with twin speaker cabinets and a 300-watt amplifier that was 100 watts louder than a Marshall

The SVT amp unit alone weighed in at 95 pounds.  Each cabinet contained eight 10” bass speakers. Although some cabs came with four 12's.

As the years went on, Ampeg changed hands several times through its history and finally St. Louis Music acquired ownership in 1986.  This is the company that brought us Electra guitars and Yairi-Alvarez acoustic guitars and many, many other products.  

St. Louis Music updated some of the amplifier line, such as the Reverb rocket, the Jet and even the Portoflex.  They also created the V series of bass amplifiers, based on the SVT. These amps sold throughout the 1980's up through the early part of this century.   At some point St. Louis Music quietly closed Ampeg production.

Barry Gordy's Hitsville USA studio in Detroit must of had an Ampeg B-15 as a studio amp.  The clip below has the bass sound of every Motown hit.

Ampeg has just introduced a 2011 version of the B-15N with two unique channels.


MSDos5 said...

I have played on there stuff but it has to much growl for Me. I had really bad luck with mesa, and am basically downsizing to a gallien kruger combo next.

Marc said...

The Ampeg B-15 is only rated at 25 or 30 watts RMS and is a tube amplifier. It works great as a recording amp, since volume can be adjusted in the mix. It is also a nice amp for Jazz players. For bass players, volume is a big hurdle when playing in a rock group or country group for that matter, which is why most of todays players choose solid state. They can pack 200 to 300 watts in a small package.

Thanks for sharing and reading MSDos5.

John Moss said...

Marc, I have a 1967 Ampeg b15n and recently blew my power tranny. I think it's probably a good idea to replace both the PT and the OT and am looking to re-pot them myself. I can't seem to find any info on the specificaions for these two transformers. If you have any info that would be helpful, hopefully the specs, I would be very grateful. Thank you